Question 1

During which phase of the cell cycle does DNA synthesis occur, and what is the consequence if this phase is skipped?

Accepted Answer

DNA synthesis occurs during the S phase; skipping this phase results in daughter cells with incomplete or missing genetic material.

Question 2

Which of the following best describes the difference between mitosis and meiosis in terms of chromosome number in daughter cells?

Accepted Answer

Mitosis maintains the chromosome number ($$2n$$), while meiosis reduces it by half ($$n).$$

Question 3

A mutation in a tumor suppressor gene can lead to cancer because:

Accepted Answer

It removes the inhibition of cell cycle progression, allowing uncontrolled cell division.

Question 4

Which checkpoint in the cell cycle ensures that all chromosomes are properly attached to the spindle before proceeding?

Accepted Answer

Metaphase checkpoint

Question 5

If a cell has 46 chromosomes at the start of the cell cycle, how many chromatids will be present after the S phase?

Accepted Answer

92 chromatids

Question 6

Which of the following is a key feature of the synaptonemal complex during meiosis?

Accepted Answer

It holds homologous chromosomes together and facilitates recombination.

Question 7

A male with an X-linked recessive disorder mates with a homozygous dominant female. What is the expected phenotype of their children?

Accepted Answer

All children will be unaffected, but daughters will be carriers.

Question 8

Which equation correctly represents the reduction in chromosome number during meiosis?

Accepted Answer

$$2n \rightarrow n$$

Question 9

In mammals, which gene on the Y chromosome is crucial for initiating male sex determination?

Accepted Answer

SRY

Question 10

Which process is responsible for dosage compensation in placental mammals?

Accepted Answer

X-inactivation

Question 11

A pedigree shows a trait that appears only in males and is passed from father to son. Which mode of inheritance is most likely?

Accepted Answer

Y-linked

Question 12

Which of the following best explains Mendel’s Law of Independent Assortment in the context of meiosis?

Accepted Answer

Alleles of different genes assort independently due to random orientation of homologous chromosomes at metaphase I.

Question 13

A cell with a mutation in a proto-oncogene that causes it to be constitutively active will most likely:

Accepted Answer

Divide uncontrollably, potentially leading to tumor formation.

Question 14

Which of the following is true regarding X-linked dominant inheritance in humans?

Accepted Answer

Affected males transmit the trait to all their daughters but none of their sons.

Question 15

What is the probability that a female carrier of an X-linked recessive trait and an unaffected male will have a colorblind son?

Accepted Answer

$$0.5$$

Question 16

Which of the following events during meiosis increases genetic diversity in gametes?

Accepted Answer

Crossing over between homologous chromosomes

Question 17

A cell is observed to have twice the normal amount of DNA but has not yet begun mitosis. Which phase is it most likely in?

Accepted Answer

G2 phase

Question 18

Which of the following is NOT a consequence of nondisjunction during meiosis?

Accepted Answer

All gametes having the same chromosome number as the parent cell

Question 19

Which protein complex is responsible for holding sister chromatids together until anaphase?

Accepted Answer

Cohesin

Question 20

In fruit flies, which chromosomal combination determines a male phenotype?

Accepted Answer

XO

Cell Division and Chromosome Heredity: Study Notes

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